Fixes aura unit tests. There were a couple of problems:

ui/aura/window.h

Index: ui/aura/window.h
diff --git a/ui/aura/window.h b/ui/aura/window.h
index a0221c4ca5278411b4ee935f114ee2f374e7c346..15573f412bdcbace9d99980d51b9d8e860c49486 100644
--- a/ui/aura/window.h
+++ b/ui/aura/window.h
@@ -40,6 +40,8 @@ class FocusManager;
 // TODO(beng): resolve ownership.
 class AURA_EXPORT Window : public ui::LayerDelegate {
  public:
+  typedef std::vector<Window*> Windows;
+
   enum Visibility {
     // Don't display the window onscreen and don't let it receive mouse
     // events. This is the default.
@@ -102,6 +104,8 @@ class AURA_EXPORT Window : public ui::LayerDelegate {
   void AddChild(Window* child);
   void RemoveChild(Window* child);
 
+  const Windows& children() const { return children_; }
+
   static void ConvertPointToWindow(Window* source,
                                    Window* target,
                                    gfx::Point* point);
@@ -137,8 +141,6 @@ class AURA_EXPORT Window : public ui::LayerDelegate {
   void* user_data() const { return user_data_; }
 
  private:
-  typedef std::vector<Window*> Windows;
-
   // If SchedulePaint has been invoked on the Window the delegate is notified.
   void UpdateLayerCanvas();